616 COAL. 



apparent combustion which it undergoes on ex- 

 posure to air, when its base has been extricated 

 from iron under water, it undoubtedly approaches 

 nearer to that element than any of the preceding 

 substances. 



It is impossible to enter here at greater length 

 into this interesting subject : the fuller details of 

 these views must be reserved for some more ap- 

 propriate place. But this sketch is sufficient to 

 show the incorrectness of those opinions in which 

 coal is considered as a compound of charcoal and 

 bitumen ; these being themselves varying com- 

 pounds of simpler chemical elements. 



The organic remains found in coal, are limited 

 to the secondary varieties, as might be expected, 

 and they consist of unknown vegetables of dif- 

 ferent kinds, which, from their general charac- 

 ters, appear to be chiefly of aquatic origin. Py- 

 rites also occurs in this substance. 



SYNOPSIS OF COAL. 



A. Burning with difficulty and without flame: 

 anthracite, when this character is perfect. 



